package com.rizzo.back.interceptor;

/*
 * Copyright 2002-2004 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import net.sf.ehcache.Cache;
import net.sf.ehcache.Element;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;

import java.io.Serializable;

/**
 * @author <a href="mailto:irbouh@gmail.com">Omar Irbouh</a>
 * @since 2004.10.07
 */
public class MethodCacheInterceptor implements MethodInterceptor, InitializingBean {

    /**
     * Field logger
     */
    private static final Log logger = LogFactory.getLog(MethodCacheInterceptor.class);

    /**
     * Field cache
     */
    private Cache cache;

    /**
     * sets cache name to be used
     *
     * @param cache
     */
    public void setCache(Cache cache) {
        this.cache = cache;
    }

    /**
     * Checks if required attributes are provided.
     */
    public void afterPropertiesSet() throws Exception {
        Assert.notNull(cache, "A cache is required. Use setCache(Cache) to provide one.");
    }

    /**
     * main method
     * caches method result if method is configured for caching
     * method results must be serializable
     */
    public Object invoke(MethodInvocation invocation) throws Throwable {
        String targetName = invocation.getThis().getClass().getName();
        String methodName = invocation.getMethod().getName();
        Object[] arguments = invocation.getArguments();
        Object result;

        logger.debug("looking for method result in cache");
        String cacheKey = getCacheKey(targetName, methodName, arguments);
        Element element = cache.get(cacheKey);
        if (element == null) {
            //call target/sub-interceptor
            logger.debug("calling intercepted method");
            result = invocation.proceed();

            //cache method result
            logger.debug("caching result");
            element = new Element(cacheKey, (Serializable) result);
            cache.put(element);
        }
        return element.getValue();
    }

    /**
     * creates cache key: targetName.methodName.argument0.argument1...
     *
     * @param targetName
     * @param methodName
     * @param arguments
     * @return
     */
    private String getCacheKey(String targetName,
                               String methodName,
                               Object[] arguments) {
        StringBuffer sb = new StringBuffer();
        sb.append(targetName)
                .append(".").append(methodName);
        if ((arguments != null) && (arguments.length != 0)) {
            for (Object argument : arguments) {
                sb.append(".")
                        .append(argument);
            }
        }

        return sb.toString();
    }
}